JUPITER, Fla. — Mariano Rivera is scheduled to announce his retirement on Saturday at a 10 a.m. press conference at Steinbrenner Field, The Post has learned.

Those briefed on the matter cautioned that Rivera has been fickle in the past about his retirement and that there was always a chance he could back out. But he has given his initial blessings to go through with the announcement on Saturday a few hours before he is scheduled to pitch in his first game of this spring.

Rivera, 43, had recently asked to speak privately with Hal and Hank Steinbrenner. It is believed that it was to tell him of his plans to call it a career after this season.

Rivera would not confirm The Post’s report after throwing a 25-pitch bullpen session Thursday at George M. Steinbrenner Field in Tampa.

“If you hear that from me, that will be confirmed,” a visibly irritated Rivera told The Post. “It’s only a rumor until I talk.”

Rivera did say there would be a meeting with the media Saturday morning. He would not comment on what he plans on saying. Rivera is scheduled to pitch Saturday during the Yankees’ 1 p.m. game against the Braves.

“Anybody else says it, it’s not true until I tell you,” Rivera said.

The Yankees said Rivera went back to New York on Wednesday for personal reasons. He was not seen in the clubhouse Wednesday.

Rivera had contemplated retirement last year but tore up his knee and vowed not to go out in that fashion. Which led to him re-signing with the Yankees in the offseason. He said earlier this spring that he knew what his plans were for the future, but was not yet ready to say what they were.

The legendary closer rehabbed the injury, and has shown no ill-effects this spring training during bullpen and batting practice sessions.

“He basically made my career in ’96 when we came up with the formula to pitch in the seventh and eighth inning,” former Yankees manager Joe Torre said. “You become a much better manager when you only have to manage six (innings).”

Rivera enters the final season of his career as baseball’s all-time leading saves leader with 608. Before last season’s injury, he had accumulated at least 30 saves in every season since 1997.

“He’s the greatest ever,” Torre said. “It’s a manager’s dream, really. It’s not a knock at the other guys, but it’s New York, the biggest fishbowl in the world, the post-season, he responded. He was more than a closer. He was a regular player for us and he was very unselfish.”

But he has saved his most dominant performances for the postseason. In 96 games and 141 innings, he has 42 saves and 0.70 ERA while winning five World Series with the Yankees.